I've read the book. The same thing still applies and I believe I've seen a video where Fung has confirmed it but I don't have the link handy.
Fasting enables us to not have to focus on calorie restrictions to see a reduction in body weight. However, if you only eat 500 calories a day, eventually you will run out of fat and your BMR will go down as you approach a lower BMI.
It's a very slow and gradual process, but it does happen. If you've got plenty of fat to burn, not a huge issue, but as you lose weight it can start to apply more.
Anecdotal evidence also suggests that people who stick with a very strict IF schedule tend to see slower results and bigger plateaus than those who change things up more often.
Right, I see what you are saying. Your BMR decreases not directly due to fasting but due to the fact that you are a lower weight. The results of fasting (weight loss) leads to lower BMR. Whereas caloric restriction shifts BMR down regardless of whether weight is lost.
I agree with your anecdotal evidence. I do 36 hour fasts 2x per week, and otherwise do 20-22 hour fasts. Every now and then I do a longer, 48-72 hour fast. I am in awe of people that get to 5-10 day fasts and hope to work up to this over time, perhaps on a quarterly basis.
Fasting enables us to not have to focus on calorie restrictions to see a reduction in body weight. However, if you only eat 500 calories a day, eventually you will run out of fat and your BMR will go down as you approach a lower BMI.
It's a very slow and gradual process, but it does happen. If you've got plenty of fat to burn, not a huge issue, but as you lose weight it can start to apply more.
Anecdotal evidence also suggests that people who stick with a very strict IF schedule tend to see slower results and bigger plateaus than those who change things up more often.